The Umbrella Academy may have secretly explained what happened to the other 36 super-powered children. The Netflix series, inspired by Gerard Way and Gabriel Bá's popular comic books, proved to be a major success when it released in early 2019, becoming the most in-demand digital original series in the US.
The first season of The Umbrella Academy began with the birth of 43 super-powered babies - children of women who had previously shown no signs of pregnancy. Eccentric billionaire Sir Reginald Hargreeves believed these babies would have tremendous potential, so traveled the world seeking out the surviving infants, attempting to persuade their mothers to give them up. He acquired seven of them and founded the Umbrella Academy in order to train them to become heroes. But what the show didn't address directly was what happened to the other 36 kids.
It's strongly implied that some of the babies died during childbirth, which makes sense given these were entirely unexpected; one birth was shown happening in a swimming pool, and another on a train. A subtle Easter egg - highlighted in Screen Rant's latest video - does suggest what may have happened to the rest of them, however. In one flashback scene, a young Leonard Peabody is shown playing with Umbrella Academy action figures, and he makes a throwaway reference to "the evil Dr. Terminal," an Umbrella Academy foe in the comics.
In the comics, Dr. Terminal was a genius inventor who was diagnosed with Einstein Syndrome, a rare (and fictional) disease that eats a person from the nervous system to the brain. He created technology that allowed him to extend the duration of his life by devouring the life-energies of others, and became one of the Umbrella Academy's recurring supervillains. Dr. Terminal is something of a stereotypical bad guy, ultimately driven by an insatiable desire to destroy the Earth.
The Umbrella Academy only featured a few flashbacks to the team's time as active heroes, and they were shown in combat against typical thugs and thieves. But the Easter egg referencing Dr. Terminal suggests that they also had supervillains to fight. It's reasonable to assume that some of these, possibly even Dr Terminal himself, were other kids who'd been born with powers. They could have been the children who survived their unexpected births, and who Sir Reginald Hargreeves failed to collect. Maybe their mothers were reluctant to give them up; perhaps local politics meant Hargreeves was unable to get to them; or maybe the children simply disappeared, given they were born all across the world, not just in developed nations where births are registered. They then grew up and lived their own lives, with some of them potentially becoming the very enemies the Umbrella Academy strove to protect the world from.
The Umbrella Academy season 2 looks set to explore the history of Hargreeves' team via time travel, which means it's possible some of their foes will soon make their small-screen debut.